Low pressure type refrigeration compressor



Spt. 5, 1939. m. ERBACH 2,171,787

LOW PRESSURE TXPE REFRIGERATION COMPRESSOR Filed Dec. 30, 1936 2 Sheets-Sheet 1 Wecfiflrback;

ZhzJeIZZ U'rJ- Sept. 5, 1939. F. R. ERBACH 2,171,787

LOW PRESSURE TYPE REFRIGERATION COMPRESSOR I 7 Filed Dec. 30, 1936 2 Sheets-Sheet 2 Patented Sept. 5, 1939 UNITED STATES PATENT OFFICE LOW PRESSURE TYPE REFRIGERATION COMPRESSOR poration of Delaware Application December 30, 1936, Serial No. 118,290

6 Claims.

The invention relates to refrigeration and has reference more particularly to improvements in a reciprocating type of compressor which will result in maintaining a pressure in the crankcase thereof above atmospheric at all times.

In a refrigeration compressor oil is supplied to the seal from the splash in the crankcase. Whenever the crankcase is at atmospheric pressure or above oil is delivered to the seal surface to lubricate the face of the seal. However, where low temperatures are required with refrigerants such as ammonia, methyl chloride or Freon, it is frequently necessary to operate at a low pressure below atmospheric. In this case the pressure outside the seal is greater than that inside and there is a tendency to pull air into the refrigeration system. This is undesirable because the air in the system will result in a high operating head pressure and generally the air brings in considerable quantities of moisture which is usually frozen at the expansion valve.

The invention has for an object to provide an improved refrigeration compressor which will maintain a crankcase pressure above atmospheric under all conditions of operation. In order to accomplish this desired result the invention contemplates replacing the oil return check valve of the compressor with a pressure relief valve and in providing a high side oil separator for returning the oil to the crankcase. In most installations of a high side oil return the crankcase of the compressor is maintained at suction pressures. In compressors embodying the invention the suction gas does not enter the crankcase and the pressure maintained in the crankcase is the mean effective pressure of the cylinder caused by the blow-by of gas past the piston.

The above structure has been found entirely satisfactory when the compressor is in operation.

However, when the compressor is at rest the high intermediate pressure in the crankcase will equalize with the low pressure in the evaporator because the gas will escape past the piston and through the suction valves of the compressor into the suction .line. This is undesirable especially in low temperature systems and is effectively solved by providing a check valve in the suction line. Therefore, the improvements of the invention maintain an intermediate gas pressure in the crankcase of the compressor during the shutdown period as well as during the operating period thereof.

With these and various other objects in view, the invention may consist of certain novel features of construction and operation, as will be more fully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference 5 characters are used to designate like parts- Figure 1 is a front elevational view, parts being shown in section, of an automotive type of refrigeration compressor embodying the features of the invention; 10

Figure 2 is an end elevational view, parts being shown in section of the compressor of Figure 1;

Figure 3 is a diagrammatic View showing the compressor of the invention connected into a complete refrigerating system of the compres- 15 sion-expansion type;

Figure 4 is a longitudinal sectional view showing the construction of the suction line check valve; and

Figure 5 is a horizontal sectional view taken 20 through the head of the compressor of Figure 1 showing the gas inlet and outlet passages and the oil return compartment.

The improvements of the invention are de signed for application to a reciprocating type of 25 refrigeration compressor comprising a body portion or casing identified by numeral I0 providing a crank case portion ll. Said portion journals a crank shaft l2 carrying a pair of connecting rods I3 which in turn connect with pistons 30v mounted so as to reciprocate within the portion 14 of the compressor. The connecting rods and piston structure is of the conventional type and is not completely disclosed as the same forms no part of the invention. Rotating with the project- 35 ing part of the shaft I2 is a seal it lubricated from the oil in the crank case through the passages ll. Also fixed to the projecting part of the crank shaft is a pulley I8 forming the driving means for rotating said crank shaft. The 40 crank case I! of the compressor provides a reservoir for oil into which the lower ends of the connecting rods l3 dip during operation of the compressor to supply oil to the connecting rod bearings and which also maintains the bearings 45 2B and the bearing face of the seal it properly Supplied with oil. Ordinarily the crank case of the compressor is maintained at a pressure above atmospheric. However, where low temperatures are required with refrigerants such as ammonia, 50 methyl chloride, Freon or sulphur dioxide, it is frequently necessary to operate at a pressure below atmospheric. In this latter case the pressure outside the seal is greater than that inside and. there is a tendency to draw air into the refriger- 55 ation system. The improvements of the invention are designed to prevent this objectionable feature in compressors as heretofore constructed and accordingly contemplates maintaining a pressure in the crank case of the compressor which will be above atmospheric at all times.

The compressor is suitably connected at 2| with the suction line 22, Figure 3, of the refrigeration system, including the condenser 45 and the evaporator 66. The evaporated refrigerant gas is returned to the compressor through passages 23 which communicate with the longitudinal chamber 24 formed in the portion I4 of the compressor. Within said chamber is located a cylindrical screen 25 for filtering the refrigerant gas or other medium returned to the compressor. Said chamber 24 communicates at its upper end with the cylindrical channel 26, Figure 1, provided by the head portion 21 of the compressor. Said head portion is provided with an internal horizontal wall 28, a lower vertical wall 30 and an upper vertical wall 3|, the latter being integral with said horizontal wall. The head portion 21 is also formed with part 32, forming a reservoir for the oil collected from the hot discharge gas, the said oil entering the part 32 through passage 33 formed in the vertical inner wall 34. The head portion 21 of the compressor is capped by member 35 and the parts are securely bolted to portion I4 by screws 36.

The cylindrical channel 25 connects chamber 24 with a plurality of inlet or suction valves 31, the said valves being arranged as shown in Figure 5, in a semi-circle to the exterior of the cylindrical portion of the vertical wall 35. On the downward stroke of the pistons the refrigerant gas is taken through the inlet valves 37 and upon the upward stroke of said pistons the charge of gas is compressed and eventually discharged through the outlet valves 38 and arranged within the vertical wall 38. Said valves are retained against their seat by coil springs 40 held in place by the member 4!. The gas discharged from the valves 38 is delivered to a chamber 42, Figure 5, which communicates with a discharge passage 43 having an outlet connection 44, Figure 2, for delivering the hot discharge gas to the condenser 45.

The head structure for a refrigeration compressor as above described is designed to separate the oil from the discharge gas while it is still hot. The oil separating from the hot discharge gas will be delivered through passage 33 to the oil reservoir comprising part 32 of the head, and which is provided with a float 46. Lever 4! pivotally supports said float from upright 48 suitably secured to the connection 49 threaded into part 32 of the head. The pin 50 is actuated by the float to open and close valve 5! which is suitably connected by means of the nipple 52 with the oil return 53. Said oil return is connected to the crank case H of the compressor at 54 and accordingly oil admitted to the return 53 is delivered to the crank case. It will be observed that the accumulation of oil in the float chamber of the compressor is subjected to the pressure of the hot discharge gas and therefore said oil will immediately be forced through the oil return 53 when said float 45 is actuated, since the pressure maintained within the crank case is intermediate the low pressure of the refrigerant gas in the suction line and the high pressure of the hot discharge gas.

A high side oil return for refrigeration compressors has generally been used on low temperature installations because low temperature installations employ in most instances a flooded low side where the oil must be separated out before delivery to the low side. However, on these installations as heretofore constructed the crank case was open to the suction line delivering low pressure refrigerant gas to the compressor and therefore the crank case was maintained at the suction pressure of the refrigeration system. In the present structure the crank case is maintained at an intermediate pressure as above described and which is rendered possible by eliminating the usual oil return check valve and substituting therefor a pressure relief valve 55, Figure 2. The pressure in the crank case is built up by the blow-by of gas past the pistons and accordingly this pressure should approximate the mean effective pressure within the cylinder. However, should the high side oil return comprising the plunger operated valve 5| and tube 53 leak there would be a tendency for the pressure in the crank case to approximate the; high pressure of the hot discharge refrigerant gas. Thus it is essential to provide a pressure relief valve such as shown at 55 in order to exhaust the gas from the crank case should the same exceed that pressure desired in the crank case.

The structure above described has been found satisfactory when the compressor is in operation but with the compressor at rest the high intermediate pressure in the crank case will equalize with the low pressure in the suction line because gas will escape past the piston and through the suction valves of the compressor into the suction line, communicating therewith. To prevent this the invention contemplates the provision of a check valve indicated in its entirety by 56, Fig-- ure 4, in the suction line tothe compressor. Said valve consists of a cylindrical housing 51 having an integral portion 58 at one end providing an annular valve seat 60 and having threaded to its other end nipple 6| having a gas passage 62. Nipple 6| provides a support for the valve 63 which is resiliently forced against the annular seat 60 by the coil spring 64. The integral portion 58 is suitably threaded to the suction line 22 and the gas passage 62 communicates with part 2| of the compressor. Therefore, in operation the low pressure refrigerant gas from the suction line must be drawn past valve 63 by suction pressure induced in chamber 24 by downward movement of the pistons of the compressor. However, when the compressor is at rest the said check valve effectively seals the suction line from the compressor. The high intermediate pressure in the crank case may escape past the piston and through the suction valves of the compressor to equalize with the low pressure in the annular channel 26 and chamber 24 but by reason of the check valve further loss of pressure from the crank case is prevented.

The invention is not to be, limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. In a refrigeration compressor having operation to compress a refrigerant gas delivered thereto at a low pressure, a suction line connecting with the compressor for delivering. said low pressure gas, a passage between said suction line and the crankcase of the compres'sorhaving a pressure relief valve therein maintaining a high pressure in the crankcase intermediate said low pressure and the pressure of the gas after compression, and an oil return connecting with the head of the compressor for returning oil removed from the gas after compression thereof to the crankcase.

2. In a refrigeration compressor having opera.- tiOn to compress a refrigerant gas delivered thereto at a low pressure, a suction line connecting with the compressor for delivering said low pressure gas, a passage between said suction line and the crankcase of the compressor having a pressure relief valve therein maintaining a high pres-- sure in the crankcase intermediate said lo-w pressure and the pressure of the gas after compression, an oil reservoir forming part of the head of the compressor for collecting oil removed from the gas after compression thereof, and means controlled by a float for returning the oil from said reservoir to the crankcase of the compressor.

3. In a refrigeration compressor having operation to compress a refrigerant gas delivered thereto at a low pressure, a suction line connecting with the compressor for delivering said low pressure gas, a passage between said suction line and the crankcase of the compressor having a pressure relief valve therein maintaining a high pressure in the crankcase intermediate said low pressure and the pressure of the gas after compression, an oil reservoir forming part of the head of the compressor for collecting oil removed from the gas after compression thereof, tubing connecting said oil reservoir with the crankcase of the compressor for returning the oil in said reservoir thereto, and a float controlled valve for said oil return.

4. In a refrigeration compressor having operation to compress a refrigerant gas delivered thereto at a low pressure, a suction line connecting with the compressor for delivering said low pressure gas, a passage between said suction line and the crankcase of the compressor having a pressure relief valve therein maintaining a high pressure in the crankcase intermediate said low pressure and the pressure of the gas after compression, an oil reservoir forming part of the head of the compressor for collecting oil removed from the gas after compression thereof, tubing connecting said oil reservoir with the crankcase of the compressor for returning the oil in said reservoir thereto, and a valve for said oil return having a float controlling the operation thereof.

5. In a refrigeration compressor of the reciprocating type having operation to compress a refrigerant gas delivered thereto at a low pressure, a suctien line connecting with the compressor for delivering said low pressure gas thereto, a check valve in the suction line, means returning oil removed from the gas after compression thereof to the crankcase, and a pressure relief valve for the crankcase, said valve exhausting into the suction line and being adjusted to maintain a high intermediate pressure in the crankcase and which will be above atmospheric.

6. In a refrigeration compressor of the reciprocating type having operation to compress a refrigerant gas delivered thereto at a low pressure, a suction line connecting with the compressor for delivering said low pressure gas thereto, a check valve in the suction line permitting gas to flow to the compressor but preventing a reverse flow of gas,an oil reservoir in thehead of the compressor for collecting oil removed from the gas after compression thereof, tubing connecting said oil reservoir with the crankcase for returning the oil to the crankcase, a float operated valve for said oil return located in the oil reservoir, and a pressure relief valve for the crankcase, said valve exhausting into the suction line and being adjusted to maintain a high intermediate pressure in the crankcase between said low pressure and the pressure of the gas after compression.

FRED R. ERBACHe 

